1. Field of the Invention
The invention relates to power connection boxes induction machines, such as medium voltage AC motors, and more particularly to terminal boxes or other auxiliary boxes capable of providing power for auxiliary devices that have operational electric power requirements differing from the motor. The terminal box has access to the induction machine incoming power and includes a power supply capable of converting the incoming power to power necessary for operation of one or more auxiliary devices, such as external electric cooling fans for medium voltage AC motors.
2. Description of the Prior Art
Induction machines, such as medium voltage AC powered electric motors, are often operated in conjunction with auxiliary devices, such as monitoring equipment, motor controls and external electric powered cooling fans that have different power requirements than the medium voltage motor. Some monitoring equipment may require 24 volt DC power. An external cooling fan may require of voltage AC power in the 110 to 220 volt range. In the past auxiliary devices required separate, parallel power sources than the medium voltage power source used to power the motor, or alternatively they could be mechanically driven by the motor shaft.
As a further example, commonly owned U.S. patent application Ser. No. 13/018,874, filed Feb. 1, 2011 is directed to an auxiliary cooling fan that is driven for by the AC motor's shaft, the entire contents of which is incorporated herein by reference. In other auxiliary cooling applications it may be preferable to drive the auxiliary fan in a manner that is not dependent upon the cooled motor's shaft speed, such as by an independently powered AC fan motor, as is shown in commonly owned U.S. Patent Publication No. 2008/0179973, the entire contents of which is also incorporated herein by reference. The independently powered AC fan motor will need its or power source, necessitating the routing of an auxiliary power line in addition to the medium voltage power lines used to power the larger motor.
Routing of one or more auxiliary power lines additional to the medium voltage power lines increases site installation complexity, as well as installation and future operational maintenance costs. For example, separate auxiliary and induction machine power lines often require separate junction boxes for connecting power to the devices powered by each line, increasing the quantity of electrical equipment that must be installed during initial system construction.
After construction, separate junction boxes for line and auxiliary power necessitate maintenance of multiple electrical connection access points for service personnel. Electrical maintenance practices often dictate that each connection access point be de-energized (“locked out”) prior to servicing equipment. Minimizing the number of electrical connection access points is desirable for reducing maintenance complexity and time.
Minimizing electrical access points is also helpful for reducing equipment reconfiguration cost and effort. In the future if auxiliary device needs change, it is possible that more auxiliary power lines or other sources will have to be routed to the site, or existing lines may need to be modified to meet the new needs. It is desirable to have electrical distribution equipment that is easily reconfigurable to meet changing operational needs.
Thus, a need exists in the art for auxiliary device power sources proximal induction machines that do not necessitate routing of additional auxiliary power lines.
A need also exists in the art for auxiliary device power sources proximal induction machines that can be modified or otherwise reconfigured to meet changing future power needs without necessity to modify or supplement existing auxiliary power lines.
An additional need exists in the art for auxiliary device power sources proximal induction machines that are pre-configured to provide designated power outputs, for example 110 or 220 volt AC power or DC power (e.g., 12 or 24 VDC), as may be needed for various auxiliary devices.